Solar and wind energy provide renewable, non-polluting energy sources, as opposed to conventional non-renewable, polluting energy sources, such as coal or oil. Because of this, solar and wind energy have become increasingly important as energy sources that may be converted into electricity. For solar energy, photovoltaic panels arranged in an array typically provide the means to convert solar energy into electrical energy.
In operating a photovoltaic array, maximum power point tracking (MPPT) is generally used to automatically determine a voltage or current at which the array should operate to generate a maximum power output for a particular temperature and solar irradiance. Generally, an array includes strings of panels, with the least efficient panel in a string determining the current and efficiency for the entire string.
Shading over a panel in a string introduces resistance in the string. Thus, the shading blocks the flow of current and lowers the power output. One such blockage in the string can lower the available power significantly. Currently available MPPT techniques can observe the available optimum power for each panel and bypass the flow of current, optimizing a cost function to maximize the power flow by “removing” the high-impedance shaded panel from a string of panels. However, while removing a partially-shaded panel increases the efficiency of the string, it also results in the inability to use the energy that is generated by the cells that are not shaded in the panel.